<template>
  <el-breadcrumb class="app-breadcrumb" separator="/">
    <transition-group name="breadcrumb">
      <el-breadcrumb-item v-for="item in levelList" :key="item.path" :to="{ path: item.path }">
        <span>{{ item.meta.title }}</span>
      </el-breadcrumb-item>
    </transition-group>
  </el-breadcrumb>
</template>

<script>
export default {
  data () {
    return {
      levelList: null
    }
  },
  watch: {
    $route () {
      this.getBreadcrumb()
    }
  },
  created() {
    this.getBreadcrumb()
  },
  methods: {
    getBreadcrumb () {
      let matched = this.$route.matched.filter(item => item.meta && item.meta.title)
      const first = matched[0]
      if (!this.isIndex(first)) {
        matched = [{ path: '/index', meta: { title: '首页' } }].concat(matched)
        this.levelList = matched
      } else {
        this.levelList = [{ path: '/index', meta: { title: '首页' } }]
      }
    },
    isIndex (route) {
      const redirect = route && route.redirect
      if (!redirect) {
        return false
      }
      return redirect === '/index'
    }
  },
}
</script>

<style lang="scss">
/* breadcrumb transition */
.breadcrumb-enter-active,
.breadcrumb-leave-active {
  transition: all .5s;
}

.breadcrumb-enter,
.breadcrumb-leave-active {
  opacity: 0;
  transform: translateX(20px);
}

.breadcrumb-move {
  transition: all .5s;
}

.breadcrumb-leave-active {
  position: absolute;
}

.app-breadcrumb.el-breadcrumb {
  margin-left: 8px;
}
</style>